Work will be conducted on three separate aspects of human color vision. Chromatic discrimination will be studied from an analytical and theoretical viewpoint, with the goal of predicting, on the basis of physical measurements, the percentage of the population who will accept a given pair of reflecting samples as a color match. Using reflecting samples that cover the entire domain of object-color perception, categorical color perception will be studied using a color naming procedure to determine the eleven basic focal colors as seen under a particular illuminant. The procedure will be extended to study color constancy, color rendering, and the limitations on naming of surface colors imposed by color-deficient vision. The relation between color-defective vision and glaucoma is the third area of study. An automated perimeter will be modified to permit the determination of shortwave-sensitive (blue) cone thresholds across the visual field in normals, glaucoma suspects, and glaucoma patients. The test may reveal early evidence of field defects in glaucoma suspects and thereby support a decision to begin treatment at a stage where visual loss is otherwise negligible; also it may prove more sensitive than current white-light procedures for monitoring the course of the disease.